The present invention is generally directed to a process and system for depositing a solid material on a substrate and for performing various processing steps (e.g. annealing, diffusion, oxidation, nitrodation, ion-implantation, etc) during the fabrication of semiconductor devices, microelectronics, optoelectronics, photovoltaic systems, flat panel display systems and magnetic devices. More particularly, the present invention is directed to various processes for producing and building layers during the fabrication of integrated circuits. The various processes of the present invention are directed to reducing processing temperatures, reducing processing time, and/or to reducing defects during the fabrication of semiconductor and other related devices.
Semiconductor devices, which are typically fabricated on a substrate, refer to devices based on the use of semiconductor materials (inorganic and organic), conductor, and dielectrics for use in a number of fields. An integrated circuit specifically refers to an electrical circuit contained on a single monolithic chip containing active and passive circuit elements. Integrated circuits and other semiconductor devices are fabricated by using various processes such as diffusion (or ion implantation), oxidation, nitrodation, annealing etc, and/or by depositing successive layers of various materials in a preselected pattern on a substrate. The materials can include semiconductive materials such as silicon, conductive materials such as metals, and low dielectric materials such as silicon dioxide, and high dielectric constant materials such as tantalum pentaoxide. Of particular significance, the semiconductive materials contained in integrated circuit chips are used to form almost all of the ordinary electronic circuit elements, such as resistors, capacitors, diodes, and transistors.
Integrated circuits are used in great quantities in electronic devices, such as digital computers, because of their small size, low power consumption, and high reliability. The complexity of integrated circuits range from simple logic gates and memory units to large arrays capable of complete video, audio and print data processing. Presently, however, there is a demand for integrated circuit chips to accomplish more tasks in a smaller space while having even lower operating voltage requirements.
As stated above, integrated circuit chips are manufactured by successively depositing layers of different materials on a substrate. Typically, the substrate is made from a thin slice or wafer of n-type or p-type silicon. The active and passive components of the integrated circuit are built within a thin n-type epitaxial layer on top of the substrate. The components of the integrated circuit can include layers of different conductive materials such as metals and semiconductive materials surrounded by low dielectric insulator materials. In attempting to improve integrated circuit chips, attention has been focused upon not only using different materials to construct the chips but also upon discovering new processes for depositing the various layers of materials on the substrate. For example, various processes and systems for depositing layers on semiconductor wafers are disclosed in U.S. Pat. No. 5,820,942, which is incorporated herein by reference in its entirety.
Currently, the semiconductor industry is switching to using larger diameter silicon wafers (12 inch wafers) in constructing the integrated circuits and to, simultaneously, reducing dimensions within each individual integrated circuit in order to increase the speed of the devices and to reduce the amount of energy needed to run the devices. These needs have created various problems for the circuit manufacturers. For instance, some of the problems and challenges ahead for semiconductor manufacturers are described in an article entitled xe2x80x9cSemiconductor Manufacturing in the 21st Centuryxe2x80x9d by Singh, et al., Semiconductor Fabtech, 9th Edition 1999, which is incorporated herein by reference.
The planned switching of the IC manufacture to 12 inch size diameter wafers provides a unique opportunity to solve some of the manufacturing problems of other related fields (e.g. solar cells and flat panel display systems). Some of these issues for developing the process and the semiconductor manufacturing equipment are described in an article and titled xe2x80x9cChanging the Rapid Thermal Processing to Rapid Photo Thermal Processing: What Does it Buy for a Particular Technologyxe2x80x9d, Singh, et al., Material Science in Semiconductor Processing, Vol. 1, 1998, which is also incorporated herein by reference.
In particular, a need currently exists for processes for producing layers in integrated circuits that reduce the number of defects that may occur in the circuits as they are manufactured. Further, a need currently exists for processes that reduce defects without increasing production times.
One known cause of defects in integrated circuits is thermal stress that results from exposing the devices to high temperatures during processing. It is believed that defects caused by thermal stress can be reduced if processing temperatures could be reduced. As such, as need also exists for a process for producing layers in integrated circuits and other semiconductor devices (e.g. solar cells) that reduces the process temperatures that have been used in the past.
The present invention recognizes and addresses the foregoing disadvantages, and others of prior art constructions and methods.
Accordingly, it is an object of the present invention to provide a process for depositing a material on a substrate.
Another object of the present invention is to provide a process for depositing and adhering a coating or a thin film of a material on a substrate using light energy.
It is another object of the present invention to provide a process for depositing layers on a semiconductor wafer or other substrates such as glass or low-cost polymer substrates.
These and other objects of the present invention are achieved by providing an apparatus and process for heating and forming layers on semiconductor wafers. The apparatus includes a thermal processing chamber adapted to contain one or more semiconductor wafers. The heating device is placed in communication with the thermal processing chamber for heating wafers contained in the chamber. The heating device, for instance, can be a plurality of lamps that emit light energy. Specifically, the lamps can emit thermal energy and optical energy. In one preferred embodiment, the lamps emit ultraviolet light, and vacuum ultraviolet light. In addition to containing a plurality of lamps, the thermal processing chamber can also contain other heating devices, such as an electrical resistance heater or the like.
In order to deposit a material or layer on the wafer, the thermal processing chamber can also include a nozzle through which a precursor material is fed. The precursor material exits the nozzle and is exposed to light energy and/or thermal energy in the processing chamber which causes a layer to form on the wafer. The precursor material can be, for instance, a liquid, a gas, or a mixture of both.
In accordance with one embodiment of the present invention, as the precursor material is fed to the chamber, the material is contacted with sonic energy emitted by a sonic energy device. In one embodiment, when the precursor material is a liquid, the nozzle and sonic energy cause the liquid to form small droplets that are directed towards the wafer.
In an alternative embodiment of the present invention, instead of or in addition to a sonic energy device, the thermal processing chamber can include an electric field for xe2x80x9cdirect writingxe2x80x9d precursor materials onto a substrate. The electric field can be created, for instance, by a focused ion beam, a focused electron beam, or by an electromagnetic field. If focused appropriately, the electric field can be used to direct a precursor material onto a wafer in order to form a pattern on the wafer. For instance, in this embodiment, a metal organic chemical vapor deposition process can be used to apply a metal to a wafer according to a desired configuration.
In still another embodiment of the present invention, a thermal processing chamber includes a stress measuring device for sensing the amount of stress present in a substrate, such as a semiconductor wafer, while the substrate is being heated and/or a coating is being formed on the substrate. For example, a controller can be placed in communication with the stress measuring device. The controller can be configured to receive information from the stress measurement device and, based upon the amount of stress present within the substrate, can control at least one parameter in the thermal processing chamber in order to reduce stress, and therefore lower defects. For instance, the controller can be configured to control the amount of thermal energy or light energy being emitted into the chamber. Alternatively, the controller can be configured to control the amount of precursor material being fed to the chamber or, when the precursor material is a liquid, control the droplet size.
Various stress measurement devices can be used in the present invention including an interferometer, an X-ray detraction device, an optical system that measures the bending or curvature of the substrate, a light source and a color monitor wherein the color monitor monitors color changes in the wafer for measuring stress, a strain gage, or an atomic force microscopy device.
The above described systems can be used not only to process integrated circuits, but can also be used to process other devices, such as solar cells. Thus, a further embodiment of the present invention is directed to a system and process for forming solar cells using a thermal processing chamber that contains a plurality of light sources. Preferably, the light sources emit thermal and optical energy, such as ultraviolet light and/or vacuum ultraviolet light. When processing solar cells, a substrate, such as a semiconductor wafer or glass substrate, can be placed on a conveyor and passed through a processing chamber. Once in the chamber, the substrate can be contacted with light energy and thermal energy originating from heating devices, such as gas furnaces. Further, the chamber can also be equipped to deposit a precursor material on the substrates in order to form various layers in the fabrication of a solar cell.